I've heard that there are odd connections between autoimmune diseases but they aren't fully understood. My father has/had lupus (it depends on who you talk to, there is a disagreement between my parents as to if it was drug induced or not), of my dad's four kids, my oldest brother and myself look like him far more than the other two. We also happen to the two kids that have IBD, my brother has Crohn's, and I have UC. My father's side has a history of various autoimmune diseases. It makes perfect sense they would connected even if not directly obvious.